On Wed, Apr 4, 2018 at 5:52 PM, David Miller <da...@davemloft.net> wrote: > From: Arnd Bergmann <a...@arndb.de> > Date: Wed, 4 Apr 2018 14:12:39 +0200 > >> The __net_initdata section cannot currently be used for structures that >> get cleaned up in an exitcall using unregister_pernet_operations: >> >> WARNING: vmlinux.o(.text+0x868c34): Section mismatch in reference from the >> function nsim_devlink_exit() to the (unknown reference) .init.data:(unknown) >> The function nsim_devlink_exit() references >> the (unknown reference) __initdata (unknown). >> This is often because nsim_devlink_exit lacks a __initdata >> annotation or the annotation of (unknown) is wrong. >> WARNING: vmlinux.o(.text+0x868c64): Section mismatch in reference from the >> function nsim_devlink_init() to the (unknown reference) .init.data:(unknown) >> WARNING: vmlinux.o(.text+0x8692bc): Section mismatch in reference from the >> function nsim_fib_exit() to the (unknown reference) .init.data:(unknown) >> WARNING: vmlinux.o(.text+0x869300): Section mismatch in reference from the >> function nsim_fib_init() to the (unknown reference) .init.data:(unknown) >> >> As that warning tells us, discarding the structure after a module is >> loaded would lead to a undefined behavior when that module is removed. >> >> It might be possible to change that annotation so it has no effect for >> loadable modules, but I have not figured out exactly how to do that, and >> we want this to be fixed in -rc1. >> >> This just removes the annotations, just like we do for all other such >> modules. >> >> Fixes: 37923ed6b8ce ("netdevsim: Add simple FIB resource controller via >> devlink") >> Signed-off-by: Arnd Bergmann <a...@arndb.de> > > Hmmm... > > __net_initdata defines to nothing if network namespaces are enabled. > > That's the whole point. > > Therefore, if NETNS is disabled, "unregister_pernet_operations" cannot > happen and this is the only time when __net_initdata actually does > something.
The problem happens with CONFIG_NETNS=n: __net_initdata turns into __initdata, and nsim_fib_net_ops is referenced from a function that is not marked __init (i.e. nsim_fib_exit). The logic to turn __net_initdata into __init only makes sense for subsystems that have no way to be unregistered, i.e. code which is always built-in, or non-unloadable modules. Arnd